If you are using a diverter or 3rd function valve then having the power off is most likely not letting them activate to relieve pressure in the grapple circuit.
I am and this does appear to be the case. I take delivery finally tomorrow and they will demonstrate the "proper" technique to avoid either side retaining pressure. They tell me quick connects on either end of the grapple hose is not needed, which I had read is how to completely eliminate the problem. We'll soon see.
Oh...temp was a non issue. We were in the shop and the tractor didnt even run for 2 minutes.